WO2003107496A1

WO2003107496A1 - Laser beam machine and control method of the machine

Info

Publication number: WO2003107496A1
Application number: PCT/JP2003/007574
Authority: WO
Inventors: 城所　仁志; 松原　真人
Original assignee: 三菱電機株式会社
Priority date: 2002-06-14
Filing date: 2003-06-13
Publication date: 2003-12-24
Also published as: CN1659751A; US20060054602A1; US7902482B2; KR20050010904A; JP3846573B2; TW200402916A; KR100698953B1; TWI223916B; JP2004022696A; CN100344033C

Abstract

A laser beam machine oscillating pulse laser includes control means for outputting instruction pulses according to the control parameter setting for controlling the laser pulse output, thinning means for inputting the instruction pulses and thinning pulses of the instruction pulses according to a predetermined set value, power source means for generating pulse power for supply to a load according to the instruction pulses output from the thinning means, and oscillation means for exciting the laser medium filled in the discharge space by discharge generated by the pulse power supplied by the power source means so as to output laser beam. The machine can prevent heating of the power source means attributed to the increase of switching count and significantly change the pulse width at a low cost.

Description

Description Laser processing apparatus and method for controlling the processing apparatus.

Technical field

The present invention relates to a laser processing apparatus that performs pulsed laser oscillation and a method for controlling a power supply apparatus that supplies electric power for generating electric discharge necessary for laser oscillation, and relates to a pulse of laser pulse output without increasing the capacity of the power supply apparatus. The present invention relates to a technique for greatly expanding the usable range of the width and expanding the processable range of the gas laser processing apparatus.

Background art

In recent years, the demand for laser processing machines that generate pulses with an output pulse width of about 1〃 s to several tens of s / s has been put to practical use for microfabrication represented by printed circuit boards.

Figure 9 shows the basic configuration of a conventional pulse laser oscillator (hereinafter referred to as a pulse laser oscillator) for a gas laser processing machine.

The command pulse group 2 output from the control device 1 controls the power supply device 3 for the pulse laser oscillator (for example, the three-phase rectifier circuit 4, the inverter circuit 5, the step-up transformer 6, etc.), and as a result, the laser Discharge occurs when power is supplied to the discharge space 7 filled with the medium (mixed gas), and the laser medium excited by the discharge is connected to the resonator 8 (electrode 9 and partial reflection mirror 1 10 and total reflection mirror). 1 1 1), and the laser beam 1 2 is output.

Specifically, when the command pulse group 2 is output from the control device 1, the inverter circuit 5 operates correspondingly, and the direct current rectified by the phase rectifier circuit 4 is operated. The power is converted into AC power, and the voltage is boosted to a voltage required for discharge by the step-up transformer 6.

Here, in a power supply device used in a gas laser processing machine (for example, a carbon dioxide laser processing machine) used for industrial purposes, the AC power supplied to generate a discharge that excites a laser medium is generally The applied voltage to the electrode (hereinafter referred to as discharge voltage) is several kV, the current that flows during discharge (hereinafter referred to as discharge current) has a peak of several tens A, and the AC frequency during discharge (hereinafter referred to as discharge frequency) is approximately several hundred kH. In the case of a pulse laser oscillator, AC power supplied to the discharge space corresponding to the command pulse group 2 from the control device 1 as shown in Fig. 10 (the number of AC components is Equivalent to the switching frequency N of circuit 5), the laser output is output.

In this specification, the electric power for causing discharge is defined as discharge electric power in this specification.

Then, one pulse and one pulse of the laser pulse output outputted in this way is irradiated to the object to be processed.

Next, the control device 1 that outputs the command pulse group 2 will be described in detail.

In a pulse laser processing machine for fine processing such as printed circuit board processing, for example, as shown in Fig. 11, laser pulse output is the main control parameter for controlling the laser output of the pulse laser oscillator. The peak output indicating the peak value, the repetitive pulse frequency indicating the frequency at which the laser pulse is output, and the pulse width indicating the pulse width of the laser pulse output are set. In addition, the optimum value of energy per pulse of laser output (hereinafter referred to as pulse energy) expressed by peak output X pulse width is determined depending on the material and processing method of the workpiece to be processed. The values for the parameters are determined.

These control parameters can be set as appropriate, and the set parameters Command pulse group 2 is output according to the event.

In the control device 1, the processing machine system is designed to output the command pulse group 2 so that the laser pulse output necessary for processing can be obtained by these control parameters. In the power supply device 3, in order to obtain the laser pulse energy required for processing, the peak of the discharge power is used to control the peak output by the command pulse group 2 output based on the control parameters set in the control device 1. To control the repetition pulse frequency, and to control the increase / decrease of switching frequency (hereinafter referred to as switching frequency) of the circuit 5 to control the pulse width.

Here, since the peak of the discharge power is mainly determined by the discharge voltage applied to the electrode 9 and the peak of the discharge current flowing by the discharge generated between the electrodes, the discharge voltage is controlled in order to control the peak of the discharge power. For example, a method of controlling the discharge current peak by controlling the inverse circuit 5 by PWM control is used.

The repetition pulse frequency is the number of laser pulses irradiated per second, and is the number of command pulses output from the control device per second.

Here, the repetitive pulse frequency is sufficiently smaller than the discharge frequency described above (that is, the switching frequency of the inverter circuit 5). For example, the discharge frequency is several hundred kHz or more as described above. On the other hand, the repetition pulse frequency is generally several kHz at the maximum. The pulse width is determined by the number of pulses in the pulse group of the discharge power output by the inverter circuit corresponding to one command pulse group. For example, if you want to increase the pulse width by 2 times (2 t) with respect to the laser pulse output with pulse width t as shown in Fig. 10, switch the inverse circuit as shown in Fig. 12 The laser pulse width is doubled (2 t) by doubling the number N of singing times (2N).

Next, Fig. 13 shows the relationship between the pulse output of the pulse laser output from the pulse laser oscillator and the pulse width.

The area represented by the peak output X pulse width indicates the pulse energy. .

The upper limit of the pulse energy is determined by the specifications of the light resistance of the total reflection mirror and the partial reflection mirror (Fig. 9) that make up the resonator part of the laser oscillator.

Therefore, for example, if the pulse energy 1 (= 1 X t 1) with the peak output pl and the pulse width t 1 is the upper limit of the energy according to the specifications of the light resistance of the mirror, the pulse width is changed from tl to t 2 (t 1 < If the pulse width is increased from t 1 to t 2 while keeping the peak output p 1 constant, the energy (2 p 1 X t 2) per pulse of the laser output will be Since the light intensity limit may be exceeded and the mirror may burn out, the pulse width cannot be simply increased. In such a case, the peak output must be reduced from p1 to p2. Yes (pl xt lp 2 xt 2). When changing the peak output in this way, the method of changing the discharge voltage applied to the electrode is generally used. However, if the discharge voltage or discharge current increases relative to the rating of the power supply, the load on the power supply increases. On the other hand, when the discharge voltage decreases, the discharge becomes unstable (discharge is difficult), and the change width of the applied voltage is usually about 10% of the rated voltage.

Currently, the processing materials and types of processing in laser processing machines are diversified, and the laser irradiation time is short (that is, the pulse width is small) as in the case of polyimide resins. Laser irradiation time is relatively long, such as those that can be processed and glass epoxy materials that contain glass fibers. (In other words, a longer pulse width) may result in better quality processing, so a pulse laser processing machine that can change the pulse width significantly is desired.

However, the conventional control method of the power supply for a gas laser processing machine has a small change width of the applied voltage. Therefore, in order to efficiently generate a discharge without exceeding the light intensity limit of the mirror, change of the pulse width is required. It had to be limited, and it was difficult to change the pulse width significantly (for example, change from less than 1 〃 s to several hundred 〃 s).

It is clear that using a mirror with a high light resistance limit is not effective in terms of cost effectiveness.

As for pulse width control, when the number of switching of the inverter circuit 5 in the power supply 3 is N, as shown in Fig. 10 and Fig. 12, the pulse width ΐ of the laser output is

t ∞ Ν

In order to increase the pulse width, it is necessary to increase the switching frequency N.

However, if the number of switching times N is increased, the switching loss of the semiconductor elements used in the power supply device increases in proportion to this, resulting in a problem that heat generation of the power supply device increases.

In this case, it is necessary to increase the capacity of the power supply itself, such as adding a cooling mechanism for the power supply and increasing the number of parallel elements and circuits. As a result, the structure of the power supply itself must be large. This is disadvantageous not only in terms of cost, but also in terms of machine installation space. Disclosure of the invention

The present invention has been made to solve the above-described problems, and provides a pulse rate. -Provided is a laser processing apparatus capable of greatly changing the pulse width at a low cost while avoiding heat generation of a power supply device due to an increase in the number of times of switching in a laser processing machine that performs the oscillation, and a control method therefor.

The laser processing apparatus according to the present invention inputs a command pulse group according to a control parameter setting for controlling the laser pulse output, and inputs the command pulse group, and sets the preset value to a preset value. Based on the thinning means for thinning out the pulses of the command pulse group, power supply means for generating pulse power to be supplied to the load in accordance with the command pulse group output from the thinning means, and pulse power supplied from the power supply means And oscillator means for exciting the laser medium filled in the discharge space and outputting the laser beam by the discharge generated by the above.

Also, the switching frequency of the inverter circuit in the power supply means is changed by regular thinning of the command pulse group by the thinning means _(and the switching cycle of the inverter circuit is changed at the rise and fall of the discharge power). It is set earlier than the constant and the fall time constant of the laser output Further, it is provided with a switching means, and sets the thinning of the command pulse group output from the control means by the thinning means.

The laser processing apparatus control method according to the present invention outputs a command pulse group according to a control parameter setting for controlling the laser pulse output, and generates a pulse power to be supplied to a load according to the command pulse group. In the control method of the laser processing apparatus that excites the laser medium filled in the discharge space by the discharge generated by the pulse power and outputs the laser light, the command pulse group is regularly thinned out The number of switching of the inverter circuit in the power supply means for generating the pulse power is changed.

According to the present invention, the laser power is maintained while maintaining a discharge voltage sufficient for generating the discharge. Can greatly increase the width

In addition, the pulse width can be greatly changed at low cost while avoiding heat generation of the power supply due to an increase in the number of switching times.

In addition, the range that can be processed can be expanded by switching according to the processing conditions. Brief Description of Drawings

FIG. 1 is a basic configuration diagram of a pulse laser oscillator based on an embodiment of the present invention.

FIG. 2 shows the command pulse group output waveform from the control device in the case of the pulse width command 2 t of the pulse laser oscillator according to the embodiment of the present invention, the corresponding discharge power waveform, and the corresponding laser pulse output. It is a waveform diagram. It is a basic block diagram.

FIG. 3 is a diagram of a circuit configuration example of the thinning circuit constituting the thinning means based on the embodiment of the present invention.

FIG. 4 is a diagram of a circuit configuration example of a thinning circuit constituting a thinning means when having a function of switching the number of thinning pulses based on the embodiment of the present invention.

FIG. 5 is a discharge power waveform and laser pulse output waveform diagram based on the relationship between the switching cycle of the power supply device and the rise time constant of the discharge power.

Figure 6 shows the discharge power waveform based on the relationship between the switching cycle of the power supply and the rise time constant of the discharge power.

FIG. 7 is a discharge power waveform and a laser pulse output waveform diagram based on the relationship between the switching cycle of the power supply device and the rise time constant of the discharge power.

FIG. 8 shows a control device setting screen based on an embodiment of the present invention and a command pulse group output as a result. FIG. 9 is a basic configuration diagram of a conventional pulse laser oscillator.

FIG. 10 is a conventional command pulse group output waveform from the control device in the case of a pulse width command t, a corresponding discharge power waveform, and a corresponding laser pulse output waveform diagram.

FIG. 11 is a setting screen example of a conventional control device, and a peak output command and a command pulse group waveform diagram output as a result.

FIG. 12 is a conventional command pulse group output waveform from the control device in the case of a pulse width command 2 t, a corresponding discharge power waveform, and a corresponding laser pulse output waveform diagram.

FIG. 13 is a graph showing the relationship between the pulse width and the laser peak output in the pulse laser oscillator. BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1.

FIG. 1 is a basic configuration diagram showing an embodiment of the present invention.

In the figure, 1 is a control device that controls laser oscillation by outputting command pulse group 2 based on the control parameters of peak output setting, repetitive pulse frequency setting, and pulse width setting, and 3 is a three-phase rectifier circuit 4 and an inverter circuit 5 and a step-up transformer 6 etc., a power supply unit for a pulse laser oscillator, and 4 is a three-phase power source that is converted into a direct current by full-wave adjustment using a thyristor etc. Phase rectifier circuit, 5 is an inverter circuit that converts high-frequency alternating current to generate a discharge necessary to obtain laser output, 6 is a step-up transformer that boosts the voltage to a dischargeable voltage, 7 is a laser medium (mixed) The discharge space filled with gas), 8 is a resonator composed of electrode 9, partial reflection mirror 10 and total reflection mirror 1 1, 1 2 is the laser beam to be output, 1 3 is in response to the pulse width command Output command buffer Thinning a predetermined amount of pulses from the scan group 2 It is a thinning circuit constituting the thinning means.

Next, the overall schematic operation will be described.

The command pulse group 2 output in response to the pulse width command set by the control device 1 is input to the thinning circuit 1 3, and a predetermined amount of pulses are thinned out by the thinning circuit 1 3 and sent to the power supply device 3. It is done.

Then, the inverter circuit 5 is operated by the thinned command pulses, and the DC power rectified by the three-phase rectifier circuit 4 is converted to AC power, and the voltage is boosted to a voltage required for discharge by the boosting transformer 6. As a result, electric power is supplied to the discharge space 7 filled with the laser medium to generate electric discharge. As a result, the laser medium excited by the electric discharge is excited by the resonator 8 and the laser beam 1 2 The laser beam output is output as 1 pulse and 1 pulse is emitted to the object to be processed.

Next, the thinning circuit 13 will be described in detail.

In this embodiment, in order to solve the conventional problem, in order to greatly increase the pulse width without increasing the number of switching times, the AC component of the supplied pulse power is supplied at a constant number and constant intervals as shown in FIG. It will be thinned out.

For example, if the pulse width t is increased twice for a pulse with t switching times and pulse width t, the pulse width is usually doubled, so the switching number N is also doubled (Fig. 10). 1 2)

However, as shown in Fig. 12, the number of switching of the chamber 5 circuit is reduced by thinning out the command pulse group 2 output from the control device 1 at the switching frequency 2 N, for example, every other pulse. The pulse width can be doubled while N is left.

The decimation circuit 13 is composed of a general logic circuit composed of flip-flops and count circuit as shown in FIG. When command pulse group 2 output from controller 1 is input from VIN of decimation circuit 1 3, the decimation pulse signal is output from VOUT.

When the thinning pulse output from the thinning circuit 1 3 corresponding to the command pulse group 2 is input to the inverter circuit 5, the alternating current of the pulse power supplied from the power supply generated by the inverter circuit 5 is obtained. The components are also output in the thinned state.

In the example, a circuit that thins out every other pulse is mentioned. However, the discharge current peak and peak output change depending on the interval of thinning out the pulses as described later. Therefore, the pulses allowed by the resonator mirrors that make up the laser oscillator Determine the number of pulses to be thinned out in consideration of energy.

Next, Fig. 4 shows an example of a circuit with a function for switching the thinning number according to the pulse width used.

In Fig. 4, two modes are provided depending on the pulse width used (for example, the short mode is set when thinning is not performed, and the long mode is set when thinning one pulse every two pulses), and it is automatically set according to the pulse width setting. The control device 1 identifies which mode it is in, and the control device 1 outputs a mode select signal so that the pulse decimation number is switched and the pulse signal is output from VOUT.

Here, the mode select signal is a logic signal (H or L) output from the control device 1 to the multiplexer 14 in the thinning circuit 1 3 according to the pulse width value set in the control device 1, for example, When the pulse width setting for controller 1 is 1 to 20 s, the short mode is selected (no decimation is performed), and the mode select signal is output from controller 1 to decimation circuit 13 as logic L. As a result, the input signal (= finger) by multiplexer 1 4 The command pulse group 2) is selected and output to the inverse circuit 5 from the thinning circuit 13.

On the other hand, when the pulse width setting is 20 s s to 40 / is, the mode select signal is output from the controller 1 to the decimation circuit 13 as the long mode (thinning one pulse every two pulses). As a result, the command pulse group resulting from the decimation by the multiplexer 14 is selected and output from the decimation circuit 13 to the inverse circuit 5.

In this way, by supplying the pulsed power in the thinned state to the oscillator part, the pulse width of the laser pulse output can be greatly expanded without increasing the number of switching times N.

For this reason, it is not necessary to increase the capacity of the power supply device 3, and it is also possible to prevent an increase in heat generation of the power supply device from the viewpoint of switching loss of the semiconductor elements used in the power supply device. This is advantageous not only from the machine surface, but also from the machine installation space.

However, when the pulse width is controlled by thinning out the pulses in this way, the switching cycle of the power supply 3 is set earlier than the rising / falling time constant of the discharge power and the falling time constant of the laser output. It is necessary to be.

Here, the rise time constant of the discharge power refers to the rise time required for the discharge power to reach the desired peak value, and the fall time constant of the discharge power refers to the discharge power from the peak value to power 0. The fall time required for The fall time constant of the laser output refers to the fall time required from the peak value until the laser output becomes zero.

The reason why the switching cycle of the power supply must be set earlier than the discharge power rise / fall time constant is as follows.

For example, as shown in Fig. 5, the discharge power is completed by switching the power supply. Assuming that 4 switching operations are required to fully start up, the discharge power P0 (t = t 1) rising by the first switching is smaller than the discharge power peak P (P0 (t = t 1) <P), The discharge power that rises in the third switching by thinning out the second switching is inherently smaller than the discharge power beak P0 (t = t3) without decimation P l (t = t3) (Pl (t = t 3) <P0 (t = t 3)) o

This relationship is not limited to the discharge current peak at the time of the third switching (t = t3), but generally holds during the discharge (Pl (t) <P0 (t), excluding t = t1) o

Similarly, after the first switching, the 2Z3 pulse is thinned out, the 4th is left and the 5th and 6th are thinned out (see Fig. 6 (a)). ), The discharge power peak P2 (t = t 7) rising at the 7th switching is smaller than the discharge power peak P l (t = t 7) when every other pulse is thinned out ( P2 (t = t7) <Pl (t = t7)), and P2 (t) Pl Pl (t) (excluding t2t1) holds throughout the discharge. 'Below, the same concept applies when thinning out three or more consecutive pulses.

However, the minimum value of the discharge power peak is the discharge power peak P0 (t = t 1) obtained by the first switching, and the number of thinning pulses that satisfies P n (t) = P0 (t = t 1) n is the limit value of the number of thinning pulses.

The same idea as above applies when thinning out one pulse after two switching operations (see Fig. 6 (b)).

Discharge power peak that rises by 4th and 5th switching by decimating 3rd switching after 2 normal switchings; Discharge power peak P0 (t 2 t 4), P 0 (t = t 5), but the discharge power peak P l (t = greater than t 5).

Similarly, the same concept applies when thinning out pulses after switching three or more times.

That is, in general, the discharge power peak decreases as the pulse interval (= the number of thinning pulses) increases, and conversely, the discharge power peak increases as the number of consecutive pulses increases. However, in any of the thinning-out methods, the discharge power peak becomes smaller than the discharge power peak P 0 (t) when no thinning is performed, and the effect of suppressing the discharge power peak can be obtained.

This means that since the laser pulse output is approximately proportional to the discharge power, the peak of the laser pulse output energy is suppressed by thinning out the AC component of the discharge power, and the problem described above, ie, the laser pulse width, is reduced. Enlarging it increases the laser pulse output energy, which is very effective for the problem of exceeding the light intensity limit of the resonator mirror. In addition, by setting the switching cycle of the power supply device earlier than the falling time constant of the laser pulse output, as shown in Fig. 7, the next switching is performed before the laser pulse output falls completely. The laser pulse output is output as a single continuous pulse without dropping.

This has the effect of expanding the pulse width of the laser pulse output. As an example, if the discharge power rise / fall time constant is about 2 fis and the laser output fall time constant is about 5 〃s, the switching frequency • is 2 MHz or more (switching cycle 0.5 S or less).

Regarding the method of thinning out the command pulse group according to the pulse width command when the set value of the pulse width is large, the hardware by the thinning circuit 1 3 Shows a circuit that thins out pulses, but the result of thinning out the number of thinning-out processing for the input pulses in the control device (that is, processing by software) However, the method is not particularly limited to the method shown in the present invention. In addition, the number of pulses to be thinned out and the ratio are determined according to the desired pulse width or the amount of laser pulse output energy, or the limit of the switching frequency of the power supply (ie, the limit of the heat generation amount of the power supply). It is not uniform and is not limited to the examples.

Next, Fig. 8 shows an example of the control parameter setting screen that is set to control the actual laser output.

In Fig. 8, in order to change the setting for thinning the command pulse according to the set pulse width, a pulse width mode item for setting the thinning number is provided, and a short mode that does not perform thinning according to the set pulse width is provided. Set the long mode to perform mode or thinning.

In response to this, the above-described mode select signal is output from the control device to the thinning circuit, and it is selected whether or not to thin the command pulse group.

Note that the switching of these modes does not necessarily have to be received as a setting item because the control device 1 may automatically switch according to the set pulse width as described above.

In this configuration, since the peak output of the supplied power automatically increases or decreases depending on whether or not the command pulse group output from the controller is thinned out, the peak output setting may be a constant value. It is not necessary.

However, this does not apply when the laser pulse output energy is finely adjusted by increasing or decreasing the discharge voltage. According to the present embodiment, the AC component of the pulse power supplied from the power supply device is thinned out at a constant number and constant intervals by the command pulse group output from the control device, without increasing the number of times of switching. The pulse width of the laser output that can be used can be greatly extended.

In addition, by controlling the peak output and the pulse width of the laser pulse output at the same time, it is possible to control the pulse laser oscillator more easily than before.

In addition, by adding a function to switch the number of AC components of pulse power supplied from the power supply device by the command pulse group output from the control device, the usage range of the pulse laser oscillator with the same power supply capacity as before is added. There is an effect that the enclosure can be expanded more than before.

In addition, when used at about 1 s to several tens of z / zs, and by decimating the AC component of the supplied pulse power at a fixed number of fixed intervals, the number of switching is increased to several tens to several hundreds S without increasing the number of switching. The machineable range can be expanded compared to the conventional case by providing a device that can be switched according to the machining conditions when the pulse width is extended. Industrial applicability

As described above, the laser processing apparatus and its control method according to the present invention are particularly suitable for use in fine processing.

Claims

The scope of the claims

1. control means for outputting command pulse groups according to control parameter settings for controlling laser pulse output;

Thinning means for inputting the command pulse group and thinning out the pulses of the command pulse group based on a preset value;

Power supply means for generating pulse power to be supplied to load t according to the command pulse group output from the thinning means,

Oscillator means for exciting the laser medium filled in the discharge space and outputting laser light by the discharge generated by the pulse power supplied from the power supply means;

A laser processing apparatus comprising:

2. The laser processing apparatus according to claim 1, wherein the number of times of switching of the inverter circuit in the power supply means is changed by regular thinning of the command pulse group by the thinning means.

3. The laser processing apparatus according to claim 2, wherein the switching cycle of the inverse circuit is set earlier than the rise / fall time constant of the discharge power and the fall time constant of the laser output.

4. The laser processing apparatus according to any one of claims 1 to 3, further comprising: a switching unit that sets the thinning of command pulses output from the control unit by the thinning unit.

5. Depending on the control parameter setting for controlling the laser pulse output Outputs command pulse group, generates pulse power to be supplied to the load according to the command pulse group, and excites the laser medium filled in the discharge space by the discharge generated by the pulse power to output laser light In the control method of the laser processing apparatus,

A method of controlling a laser processing apparatus, wherein the number of switching of an inverter circuit in a power supply means for generating the pulse power is changed by regularly thinning out the command pulse group. ·